Molded balsa article



Aug 7, 1945. V D. NEWMARK 2,381,134

MOLDED BALSA ARTICLE Filed April 11, 1944 HTFOlP/VEY Patente'd Aug. 7,i945 TED STATES rA'rE 'r OFFICE David New r nfa rfilfifw xi Nfif52:11.), f

halitoW iliiam Kramer, New York, N. Y.

1 Claim.

' of balsa wood into hollow or solid structures and my improvement isdirected to the utilization of the compressible nature or balsa for theproduction or a variety of objects, such for example as model airplaneiuselages and wings, mtdel ship hulls, doll heads, fishing lures, duckdecoys and other hollow or solid articles.

Heretofore balsa has been used in sheet form as well as in whittledblock form for the production of diilerent. articles, but to the best 01my knowledge and belief it is new with me to take advantage of thecompressibility of balsa tor molding it in a moist'state under pressure,at a suitable degree of heat. This I consider my dismold elements beingat the desired temperature and all the balsa parts having been subjectedto the adhesive solution.

covery and in my practice I have for example been able to compress balsasheet plies into deep extrusionsand corners, to the extent of shaping amodel ships hull of commensurate depth for such a structure.

In carrying out my invention 1 takethin sheets of balsa, allconsiderably smaller than the mold itself, such sheets for examplehaving a thickness of 1; inch, impregnate them with a solution'of urearesin, or-other suitable adhesive, and place. these-sheets in a femalemold; the ends of the sheets may be overlapped. A series of layers areused to achieve any desired thickness. Then the male mold is pressedinto the female mold under sufficient pressure to compress theinterposed ply sheets whereupon compression and extrusion occur. y

In practice I have found that a pressure oi 200-360 pounds to the.square inch is sumcient tor the purpose.

The mold members are subjected/to a certain degree of heat; such forexample as 200 F., so that-t e process of molding balsa comprises theamp oyment of heated. molds in which the adhesive impregnated balsa. isby pressure compressed into desired extruded conformations.

, shape and contours established by the die cut- The small strips orpieces of balsa, disposed at random with the balsa sheets in the femalemold, have the efiect of actingas binders under compression pressure,thereby serving to strengthen or reinforce the molded mass of the formedobject.

Other features and advantages will hereinafter appear.

In the drawing- I I Figure 1 is a perspective view of a female member ofa mold or die, with balsa parts or slats shown placecLtherein.

Fig. 2 is a cross-section of Fig 1.

Fig. 3 is a cross-section of a complete mold or die.

Fig. 4 is a uct. v

Fig. 5 is a side elevation of a molded airplane fuselage, and

Fig. 6 is a section on the line 6-8 oi. Fig. 5.

In Figs. 1 to 3 let i indicate the female mold or diepart employed by mein molding the hull oi myinvention portions of toy ships, and, in Fig. 3there appear the male mold or die part 2..

pieces of balsa 3, which slats or pieces have previously beenimpregnated and thus moistened with a suitable adhesive solution, andthen into the male mold part 2' is entered the female mold part underdesired applied pressure. both mold parts being heated to asuitabletemperature, for

the purpose of compressing the contained balsa.

pieces or slats and thereby molding them to the ting in'the mold parts.

Because of the compressibility of balsa I have thereof, into the femalemold, as for the purpose found it'practicable to introduce small stripsor pieces of balsa, together with the sheets or leaves It should beappreciated that the compressible characteristic of balsa, not possessedby other ployed in the manner'indicated.

. In addition to the strips or slats 8 of balsa placed in the mold thereis added a quantity oi woods, is what enables this material to beemrelatively small pieces 4, care being used to. have of filling outsharp corners in. said mold. to the end that the object to be moldedwill acquire its completed form and contour in the molding operation. Ashas been stated the inherent compressibility, of balsa under the moldingconditions set forth, enables these small strips'and pieces the sharpcorners of the mold fliled'with thesesmall pieces, and then the press isclosed.

. The small pieces are really in "suspension" in the pile and are notfa-flected by the die until ac tual contact is made. If large sheetswere used to become, as it'were, homogeneously welded in with the balsamass in, the female mold as comthey would be apt to be in contact withthe male die before the press was closed, thus causing the sheets totear. The small strips, laid willy-hilly pressed under pressure by the"male mold, these in the female mold, form the basis of the astop planview of a completed prodbalsa wood which consists in impregnating balsastrips including relatively large and small pieces with an adhesivesolution, placing said moist strips between female and male mold memberswith the small pieces adjacent the mold comers,

applying heat at around 200 F. to said mold members, and subjecting saidbalsa strips to 'a compression pressure of from 200 to 300 pounds persquare inch to accord the compressed mass is desired extrudedconformation.

DAVID NEWMARK.

